The invention relates to a rack store for storing items in storage locations of racks, wherein at least one rack lane is formed between at least two racks, and wherein first guide tracks are provided substantially in the direction of the racks and second guide tracks are provided substantially transverse to the racks, on which guide tracks at least one rail vehicle can be moved in a controlled manner by control means for storing and removing items.
Patent application WO2014/204 300 A1 discloses such a rack store with control means for controlling the path, which a rail vehicle should take for storing and removing an item. Depending on how dense the traffic of rail vehicles is on individual guide tracks and intersection points of guide tracks, or, respectively, how dense it is planned to be by the control means, the control means identify them as “blocked” or, for example, as “fit for traffic in a directional way only at a certain speed”. This is supposed to serve for ensuring an operation of the rail vehicles on the guide tracks for storing and removing items which is as smooth as possible. However, it has turned out to be a disadvantage of said known rack store that the control means are very complex and thus prone to failure and fail to achieve the throughput required for high performing stores.
If items are removed from a rack store, such as the rack store disclosed in WO2014/204 300 A1, toward a picking station, they should be removed from the rack store and placed onto the materials handling equipment in an already sorted manner, if possible, so that as little as possible has to be sorted on the materials handling equipment. For this purpose, the control means actuate the rail vehicles such that the rail vehicles will fetch the items consecutively from the individual storage locations, according to the desired sorting, and will deliver them to the materials handling equipment via a lift, whereupon the materials handling equipment will convey the sorted items to the respective picking station. However, because of “blocked” guide tracks, defective rail vehicles or other circumstances, it may happen that the items cannot be removed from the rack store with the requested sorting. For this reason, a so-called pre-zone must be implemented in front of the rack store as part of the materials handling equipment, in which pre-zone it is possible to sort the items, for example, by a materials handling equipment guided in a circle, before the sorted items are discharged from the materials handling equipment guided in a circle and are conveyed to the respective picking station. However, in doing so, the lifts of the rack store and the sorting in the pre-zone form a bottleneck limiting the throughput during the removal from storage, since all the items removed from the various rack levels of the rack store have to be sorted in the materials handling equipment guided in only one circle.